The Earthship greenhouseis not just designed to provide a space to
collect natural heat and light from the sun. It is also intended to be used as
a greenhouse for growing your own food. The plantsin the greenhouse are fed by a greywater
system that uses reclaimed showerand sink water to water the plants, which then
clean the water for use in toilets later. That is a cool idea! In the Earthship
literature and books, it is emphasized that that the Earthship greenhouse can
grow “all the food you need to survive.”

Of the people whose Earthships we surveyed, who we interviewed,
who commented on blogs or forums, or who answered our surveys… none were able
to corroborate this ideal. Certainly the greenhouses can provide some food. But, the people we spoke to
said that they could not grow their own food in sufficient supply to say they
were provided all they need. They used grocery stores, farmers markets, or CSAs
as their primary source of food. The Earthship greenhouseserved as a supplemental resource, and only
seasonally, in many cases.

An architect who blogs anonymously was in the audience at
one of the Earthship lectures in Australia. Afterwards, he reported in his blog
that he struggled with the lifestyle and thermal performancedata presented, as the presentations implied
the information presented was an “undisputed truth” when in fact some of the data
presented showed clearly that there were issues with performance. But, people
would have to know what to look for in order to determine what parts were
concerning. (This is why we attempt to explain the width and breadth of the
researchin Chapter
2.) He went on to question if the fish or water plantsin the pond systems used for aquaponics were
edible. He then calculated that in order to eat fish in the recommended dietary
amounts of three times a week, you would need to harvest at least 12 fish each
month. Clearly that would require a large and sophisticated system, which would
put this ideal out of reach for the scale and budget of most Earthships.

This vision of providing all we need through maximizing the
value of our space is awesome. We get it. We do. But it does not seem possible
to produce enough foodworking at
the scale of a single Earthship to meet this ideal.

According to the researchcompleted by Kruis and Heun in 2007, a family
of four living in an Earthship would require 98 gallons (370L) of water per
day, or 37,500 gallons (135,000L) of water per year. They identified in their
research that the water requirement was totally achievable in a wet place like
Michigan, but those quantities could not be achieved in Hawaii, New Mexico, or
Alaska. This corroborates our experience in Taos where most of the Earthship
owners we know have to buy water. This makes a backup dependable water supply
essential for many locations.